1. Field of the Invention
This invention relates to the field of attachments for power tools, especially to an abrading device for attachment to a portable rotary power saw.
2. Description of the Prior Art
Various devices have been conceived for changing the normal operation of a power tool to accomplish some other operation. Most frequently, such devices are based upon the motor of an electric drill, which has a convenient chuck to engage or disengage a driving shaft of some other power tool. Examples of such adaptations of power tools are seen in U.S. Pat. Nos. 1,850,137--Pursell, 4,118,897--Martin, and others.
Also known in the art are devices which purport to make a universal power tool from a motor and means for attaching the motor to a variety of cutting or abrading devices. In U.S. Pat. Nos. 1,663,486--Wertz and 1,779,031--Casey, universal tools are disclosed in which rotary saws are one of the options provided for mounting the motors and parts.
U.S. Pat. No. 4,033,035--Trimmer discloses an attachment device for a portable rotary power saw, in which the rotary power saw is altered to function as a chain saw. As disclosed, the device is said to be useful for beam cutting and mitering. The usual rotary saw blade is removed and the saw housing is attached to a support plate which carries a chain saw attachment including a sprocket and track for supporting a toothed roller chain. In order to tension the chain saw, that is, to pull the chain against its track, the rotary saw's capability of adjusting the depth of the cut of the saw blade is employed. Specifically, the platform upon which the rotary saw usually rests is clamped to a support platform for the attachment; the chain is run over a sprocket on the saw motor shaft; and, the rotary saw is rotated up around its pivot pin to space the motor shaft from the track, thereby tightening the chain. This device employs the vertical adjustment capabilities of a rotary saw, but only for tensioning. The device merely attaches a different form of saw blade, a toothed chain rather than toothed disk, to the same point of attachment on a rotary saw, and with the same stresses as are characteristic of the rotary saw.
U.S. Pat. No. 2,676,624--Gecmen discloses another version of an attachment for a rotary saw. In Gecmen, a supplemental supporting structure is attached to the platform of a conventional rotary power saw, such that the saw can be made to trace a cut at a predetermined distance from an edge of a board or the like. Thumscrew clamps attach the various parts of the Gecmen device, but the blade remains in place. No attempt is made to engage the power-producing element, namely the saw motor.
The present invention adapts the conventional high powered portable rotary power saw to a situation in which an abrading wheel, planing wheel or similar working wheel is to be applied with a transverse force to a point which is axially spaced from the usual position of the saw blade in a rotary power saw. The axis of rotation is adjustable using the power saw adjustment, and the transverse force applied in use is directly opposed notwithstanding the adjustment capability. The saw is vertically-adjustable by rotation around a pivot point spaced from axis, such rotation causing displacement along two axis in the plane. In other words, vertical adjustment of the working wheel is accomplished such that the axis of rotation can be both raised with respect to the working surface, and also moved forward and backward relative to the attachment structure, thereby maintaining the mount for the end of the shaft carrying the working wheel along the axis of the power source.
According to the invention, a preferably length-adjustable shaft is affixed to the saw motor in place of the usual saw blade and the support table of the saw is attached to a support platform which carries an adjustable rotation mounting for an opposite end of the working shaft. Preferably, the movable rotation mounting is a pivotal, slidable adjustment arm which can be manually adjusted vertically using a thumscrew. According to the invention, the high power capabilities of the rotary saw can be usefully applied to drive an attachment device in which transverse pressure is applied to the working shaft primarily at a point which is spaced from the conventional mounting point of the saw blade, without dangerous vibration or undue wear on the saw, its mountings and the attachment structure.